vintageHIWATTconvention.com

Hello, well some of you may remember that I got this '70 DR504 with some dirty mods on it. Well the restoration duty goes pretty well so far... I have 3 questions for ya :

- Filter caps : they all look original, 1 is bulging right now ... should I replace them all ? or just that particular one ?
- On the power section, a stock 504 came with 160uf/63v capacitor... Here, I have 2x 100uf/63v in series.... what should I do ? keep 'em there ? remove 1, or remove both and replace with single 160uf/63v ?
- V3A Cathode Capacitor (usually 47n) : what's the purpose of this cap ? not on mine, but "optional" on mid 70s schematics... ?

make sure you follow LATE 1970's Schematics. your amp is a very late 1970's.

a 100uf bias cap will work fine in place of a 160uf.

If you are going to gig the amp very regularly, then recap it completely.

Dr.HIWATT wrote:make sure you follow LATE 1970's Schematics. your amp is a very late 1970's.

a 100uf bias cap will work fine in place of a 160uf.

If you are going to gig the amp very regularly, then recap it completely.

Yeah, of course Im using the Late 70s schematic... however, sad thing is that MHUSS havent posted a late 70s layout on his website... only the early and mid 70s versions. Is there a particular reason for this ?

Can someone englighten me about the 47n V3A Cathode cap, and what it does ?

We should all be very appreciative that his site exists at all. Mark is a very busy guy, working and teaching college courses, playing in a band and trying to find time to help out HIWATT folks in his "spare" time. "Does he have any spare time?"

Dr.HIWATT wrote:We should all be very appreciative that his site exists at all. Mark is a very busy guy, working and teaching college courses, playing in a band and trying to find time to help out HIWATT folks in his "spare" time. "Does he have any spare time?"

oh! Dont worry, I already DO appreciate his work and contribution !!
I was just wondering simply.

Filter caps : they all look original, 1 is bulging right now ... should I replace them all ?

replace them all ... the vhr kit will give you everything you need ... i did that with my 79 504 with no complaints

Do them all together and then there is no need to worry about them ... besides, it's not that much $$

j

My original thought in doing the layouts was to aid builders, and not many (any?) people build the late 70's preamp. However, the restoration angle is an important one, that had not occurred to me until now.

If anyone has the time and artistic skills to do a late 70's layout, I'll be happy to put it up.

--mark

mhuss wrote:My original thought in doing the layouts was to aid builders, and not many (any?) people build the late 70's preamp. However, the restoration angle is an important one, that had not occurred to me until now.

If anyone has the time and artistic skills to do a late 70's layout, I'll be happy to put it up.

--mark

Mark, that is exactly what Im doing. I'll work on it this week.
Which software have you used for the layouts ? I can use something like Illustrator or similar here, do you have any "master" files ?

I just used a generic graphics program, so there's no better source than the PDF/jpb files unfortunately.

--mark

+ 1 for the late '70s layout! I'm in the midst of restoring my FL112. MH site is a great resource (as is this one).